The FLEX21 Thermistor Assemblies are used to monitor temperature at eight locations. One is used to monitor the vessels' temperatures and is marked 46. One is used to monitor the reference temperature surrounding the round bottom flasks and is marked 47. Four of these are used in the round bottom flasks and are numbered 50, 51, 52, and 53. One is used in the oven and is marked 54. One is used in the evaporation inlet and is marked 55. Specify 46, 47, 50, 51, 52, 53, 54 or 55 at checkout.